I have developed a keen interest in the neurophysiology of the central nervous system over the last few years, particularly in pediatrics. This interest arose from my experiences in clinical neurophysiology, both in adults and in pediatrics. Over the last two years I have become interested in motor development and the effect of motor system diseases upon development and outcome of patients. In the next 5 years I would like to investigate the cortical representation of the motor system in the pediatric population, the effect that particular diseases have upon this cortical organization or reorganization, and the effect of rehabilitation on the motor cortex representation. Using cortical magnetic stimulation and mapping the motor cortex of normal children, its cortical representation can be localized. The next step would be to compare the cortical maps of children with motor system diseases and lesions. The types of disease processes I am interested in would include hemispherectomy for epilepsy, stroke, cerebral palsy (cortical), and traumatic quadriplegia (subcortical). By comparing the cortical maps of the patients to our normal subjects, the question of cortical reorganization can be addressed and any differences between cortical and subcortical lesions can be looked at. The effects of different rehabilitative therapies can be evaluated in relation to the differences in the cortical maps and functional outcome of these patients. The use of the cortical mapping by cortical magnetic stimulation may then be useful in guiding treatment. These projects will be undertaken at the Boston Children's Hospital through the neurology department and neurophysiology laboratory. The normal subjects and patients will come from the outpatient clinics. The magnetic stimulation will be performed in the neurophysiology laboratory which has just purchased a magnetic stimulator.